The donation came after Abramoff pleaded guilty to corruption charges and agreed to cooperate with a federal corruption investigation in Washington.

"The speaker believes that while these contributions were legal, it is appropriate to donate the money to charity," a spokesman for the Illinois Republican, Ron Bonjean, said. Bonjean did not specify which group or groups would receive the money.

Abramoff pleaded guilty to conspiracy, fraud and tax evasion charges in an agreement with federal prosecutors that could have a wide-reaching effect in Washington. (Full story)

Abramoff is a former College Republican chairman with longstanding ties to top Republicans in Washington, including former House Majority Leader Tom DeLay, conservative activist Grover Norquist and former Christian Coalition chief Ralph Reed.

A source close to the probe said investigators are looking at about a half dozen members of Congress, while a senior government official told CNN the probe involves about two dozen lawmakers and staffers.

Sources told CNN that Abramoff might have thousands of e-mails in which he describes the influence-peddling in which he was involved and explains what lawmakers were doing in exchange for the money he was putting into their campaign coffers.

Abramoff's guilty plea comes as Democrats head into the 2006 congressional elections by blasting what they call a "culture of corruption" surrounding the Republican leadership.

About two-thirds of the more than $4.4 million in political donations from Abramoff, his clients and associates since 1998 went to Republicans, according to records compiled by the Center for Responsive Politics, a campaign-finance watchdog group. A search of Federal Election Commission records since 1998 found no personal donations from Abramoff to Democrats.

Republican Sen. Conrad Burns of Montana told The Washington Post in December that he would return $150,000 in contributions from Abramoff, his clients and associates. Burns is up for re-election in November, and state Democrats have been hammering him over his ties to the lobbyist.

DeLay's political action committee, Americans for a Republican Majority, has returned $5,000 from Abramoff, according to federal election records. The Texas congressman gave up his leadership post in September after his indictment on charges that he improperly steered corporate money into the state's 2002 legislative races -- a case unrelated to Abramoff's. DeLay's trial in Texas on money laundering charges is pending. He has pleaded not guilty.

And North Dakota Sen. Byron Dorgan said in December that he would return $67,000 in donations from Indian tribes Abramoff represented. Dorgan, the ranking Democrat on the Indian Affairs Committee that investigated Abramoff's dealings with his tribal clients, told a North Dakota newspaper that he would not keep any money that "could have been the result of any action Mr. Abramoff might have taken."

He praised the Justice Department for securing Abramoff's plea agreement, saying in a written statement Tuesday that it "confirms much of the work that we have done and much of what we have found."